Zeitschrift fur Naturforschung. Section C, Biosciences最新文献

The patterns of the anterior lateral-line afferents of Lampetra fluviatilis as revealed by transganglionic transport of horseradish peroxidase are described. The afferents form two roots in entering the rhombencephalon. Fibers of the dorsalmost root can be traced to a short dorsal fascicle which runs along the dorsal nucleus. The ventral roots form two fascicles adjacent to the nucleus intermedius. Comparison with urodeles indicates that lampreys, like urodeles and other anamniotic vertebrates are electroreceptive.

The enzymic hydroxylation of phenylalanine by phenylalanine hydroxylase (E.C. 1.14.16.1.) in vitro is dependent on the presence of hydrogen peroxide removing processes. The loss of phenylalanine hydroxylase activity can be prevented to the same extent by catalase as well as the presence of optimized amounts of both peroxidase and superoxide dismutase. Peroxidase alone exhibited only two third of the maximal protective effect of catalase whereas superoxide dismutase alone was not able to exert any protective influence on phenylalanine hydroxylase. These findings suggest that the termination of phenylalanine hydroxylation in the absence of hydrogen peroxide removing reactions is probably due to destructive oxygen species generated at the active site iron of phenylalanine hydroxylase in the presence of H2O2 and the tetrahydropterin cofactor.

Three different methods for the determination of phenylalanine hydroxylase activity have been compared: a) Differential photometric assay of the increase in tyrosine concentration in the presence of phenylalanine; b) Product separation by thin layer chromatography and scintillation counting of the [14C]tyrosine formed; c) HPLC separation and spectrofluorometric quantification of derivatized amino acids. A comparison of the activities of phenylalanine hydroxylase in rat liver and Euglena gracilis clearly showed that only rat liver contains this enzymic activity as shown by methods b) and c) although pseudo-activity of Euglena gracilis preparations was found during the spectrophotometric test a). The HPLC method proved to be the fastest, most reliable and convenient method for direct tyrosine determination and thus for measuring phenylalanine hydroxylase activity.

Continuous flow 13C NMR spectroscopy has been used for the first time to monitor the metabolism of a 13C labeled drug in an isolated liver. Continuous and almost immediate information on the metabolite formation could be obtained using 13C labeled phenacetin without alteration of the biological system. The data are consistent with those observed by conventional techniques (HPLC, aliquot 13C NMR measurements). From the biological point of view the sensitivity of continuous flow 13C NMR spectroscopy is still low (10(-3) M). The results presented demonstrate however that non-invasive and non-radioactive real time monitoring of drug metabolism in intact organs is possible.

The incubation of erythrocyte ghosts with mixtures of vitamins A+D3, A+E, A+K1 produces decrease or increase of fluorescence anisotropy r of the DPH probe, depending on the vitamin/vitamin ratio. We found a correlation between the order parameter S and cell fusion phenomena observed by phase contrast microscopy.

At lower concentrations, polyarginine, polylysine, protamine, histones H1, H2A, H2B and H3 cause lysis of human erythrocytes, whereas at higher concentrations inner histones are not hemolytic but induce only surface condensation and alterations in the cell-shape. Antibody coated erythrocytes treated with polyarginine result in ghost-like spheres having globular bodies 1 micron in diameter on the surface. Human fibroblasts and lymphocytes, and Ehrlich ascites cells treated with polyarginine also form surface globular bodies similar in size. Nucleate cell-polyarginine mixtures with lower polycation doses result in cytolysis, while higher polycation doses produce pyknosis of the cell surface accompanied by reorganization of a membrane-like structure. Changes in spectrofluorometric values result from 1,6-diphenyl-1,3, 5-hexatrien binding to cell lipids, match the plasma membrane alterations. Reciprocal shake incubation amplifies and/or conditions these polycation-induced alterations. The homogeneity of pyknotic surface bodies and the apparent polycationic membrane reorganization requiring oscillatory friction forces suggest the preexistence of a multizonal glycocalyx distribution corresponding to plasma membrane compartments. The possible role of this compartmentalization in receptor and membrane recycling, as well as the involvement of reversible catalytic-like polycation condensation in macromolecular changes are discussed.

1H double-quantum and COSY NMR-spectra of the porcine protein adenylate kinase have been obtained in order to assign aromatic spin systems within this protein, which contains seven tyrosyl, five phenylalanyl, and two histidyl residues. Double-quantum spectroscopy in its simple form allowed the assignment of five connectivities in the aromatic region and therefore proved inferior to COSY, which allowed the assignment of connectivities within nine aromatic residues.

To get further insight into the causes of differences between rat splenic and thymic cells with regard to DNA repair synthesis, scheduled (SDS) and unscheduled (UDS) DNA synthesis as well as nucleoid sedimentation of the cells were investigated under the influence of ethidium bromide (EB, 1-1000 micrograms/ml). - At concentrations of greater than or equal to 25 micrograms/ml, EB inhibited SDS of both cell species and UDS of thymic cells; much higher additions of the drug (greater than 200 micrograms/ml) were needed to diminish UDS of splenic cells, lower EB-concentrations (25-175 micrograms/ml) stimulating the UDS of the splenic cell preparation. - The sedimentation rate of splenic and thymic cell nucleoids within neutral sucrose gradients had a biphasic dependence on the EB-concentrations. As compared to thymic cells however, preincubation of splenic cells with 50-250 micrograms EB/ml resulted in a significant greater (15-30 percent) sedimentation distance. - The results suggest that a relationship exists between the stimulation of UDS and the ability of cells to establish a greater DNA compactness in the presence of EB.

The work reported here concerns the specificity of four antibodies elicited by synthetic peptides corresponding to three domains of the HLA-B7 glycoprotein, and one of the beta 2 microglobulin. One of the four peptides had been previously investigated, but the data obtained by its elicited antibodies were uncomplete. Of the three HLA-B7 peptides assayed, one was unable to raise an immune response. The other two produced antibodies in good titer that reacted with the antigen peptide, but were unable to recognize antigenic determinants when tested on membrane glycoproteins solubilized from human lymphoblastoid cells. In contract, the antibody elicited by the only fragment from the beta 2microglobulin recognized the native beta 2microglobulin molecule as well as HLA/beta 2m complexes, and reacted with intact human cells, as determined by ELISA and by FACS analysis. This peptide, which contains one of the most hydrophylic fragment of the whole molecule, is likely an important antigenic site, since it is also recognized by traditional antisera raised against native beta 2microglobulin.

A method is described for the partial purification of a granulomonopoiesis inhibitor derived from 200 l-batches equivalent to 1 kg or 2 X 10(12) leukocytes of porcine blood. Serum-free conditioned media were concentrated and separated via ammonium sulfate precipitation, acetone partitioning, ultrafiltration and gel chromatography. The active substance revealed a molecular mass of 500-700 Da and was not thiol-dependent, thus contrasting it with previously-reported granulopoiesis inhibitors. Inhibition of colony formation in an in vitro myeloid stem cell assay using various colony-stimulating factors showed that mature granulocytes and monocytes were equally affected. Apparent lack of cytotoxicity was suggested using a new reversibility test.